They are among the most prized treasures held by the Royal Collection, the British Museum and the Ashmolean in Oxford. But drawings that are said to give an unparalleled insight into the creative process of Michelangelo should no longer be attributed to him, according to new research.

Three academics from the Universities of Leipzig and Hamburg have written a five-volume study that casts doubt on the works held in Britain, which are among up to 40 per cent of the world’s Michelangelos that they believe should be dismissed as copies. The three academics argue that hundreds of drawings by Michelangelo cannot be circulating worldwide when contemporary accounts refer to the artist burning most of them. The three are also publishing a recently discovered contemporary document that explains how so few drawings by Michelangelo survived after his death. Its contents are so dramatic that one journal tried to suppress it, they claim.

Frank Zöllner, a professor of Renaissance and Modern art at the University of Leipzig in Germany, said: “Scholars try to attribute an enormous amount of drawings to Michelangelo . . . Those people who believe in the large corpus are those active on the market or curators in public collections who have large Michelangelo holdings.”

The findings of the academics, who also include Dr Thomas Pöpper, a lecturer in art history at Leipzig, and Christof Thoenes, an honorary professor at the University of Hamburg, will be published by Taschen in Michelangelo: Complete Works, on November 19.

Their study casts doubt out on a number of sheets in the Royal Collection, including The Risen Christ. Dr Pöpper commented on the the right hand of the figure and its pentimenti, the lines that indicate where an artist has changed their mind. “The drawing reveals what, for Michelangelo’s draughtsmanship, is a suspicious number of pentimenti, which might in fact be traceable to the copyist.”

It pales, Professor Zöllner added, against another study for The Risen Christ in the British Museum: “I have no doubt about this one. Its lines were drawn by someone who was drawing from a model or life. The other one [The Royal Collection] is a drawing after a drawing.” Nor are these academics convinced by another sheet in The Royal Collection, the Three Labours of Hercules. Dr Pöpper said that, while the individual scenes have been developed to noticeably different degrees, Michelangelo would not have created such a frieze on a single sheet. Turning his attention to a drawing of the Crucifixion in the British Museum, he said that it reveals a certain pedantry and a hesitation in the handling of line, arguing “strongly in favour of a copyist”. He is also unimpressed by a sheet with two sketches for The Brazen Serpent in the Ashmolean Museum, in Oxford. Dr Pöpper believes that it is a copy of a lost original, a theory that is “supported by aspects of its technique”.

A spokeswoman for the Royal Collection said: “Royal Collection curators have no reason to doubt the widely and generally accepted attributions of these drawings to Michelangelo.”

Hugo Chapman, the curator of Italian drawings for the British Museum, said: “The Crucifixion drawing is to me one of the most amazing and moving drawings in Western art.” But he added: “I’m all for a healthy debate. Nothing is written in stone.”

Timothy Wilson, of the Ashmolean Museum, said: “The Ashmolean is a university museum and welcomes intelligent and informed debate about all aspects of works of art in its care.”

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